There is increasing demand for services of monitoring elderly people, children or other people, and various monitoring systems that make use of devices etc. having a sensor are proposed. For example, a system that monitors statuses, such as sitting up, getting out of a bed, etc., of a patient in a hospital room or his or her own room is proposed. Further, a method of determining (or estimating), from the communication condition of a wireless communication device, whether the user is in or out of an area in which communications are possible is proposed (Japanese Laid-open Patent Publication No. 2014-179819).
However, monitoring targets such as elderly people, children or other people do not always stay in a particular room such as a hospital room, his or her own room, etc., depending upon his or her health condition. Thus, it is desirable to be able to provide a monitoring service over a wide area. However, it is difficult for methods that use a sensor or an RFID (radio frequency identifier) as disclosed by Japanese Laid-open Patent Publication No. 2014-179819 or other publications to provide a monitoring service over a wide area.